/*
 * $RCSfile$
 *
 * Copyright 2004-2008 Sun Microsystems, Inc.  All Rights Reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Sun designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Sun in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
 * CA 95054 USA or visit www.sun.com if you need additional information or
 * have any questions.
 *
 * $Revision: 127 $
 * $Date: 2008-02-28 20:18:51 +0000 (Thu, 28 Feb 2008) $
 * $State$
 */

package toxi.geom;

/**
 * Utility vecmath class used when computing the hash code for vecmath objects
 * containing float or double values. This fixes Issue 36.
 */
class VecMathUtil {

    /**
     * Returns the representation of the specified floating-point value
     * according to the IEEE 754 floating-point "double format" bit layout,
     * after first mapping -0.0 to 0.0. This method is identical to
     * Double.doubleToLongBits(double) except that an integer value of 0L is
     * returned for a floating-point value of -0.0. This is done for the purpose
     * of computing a hash code that satisfies the contract of hashCode() and
     * equals(). The equals() method in each vecmath class does a pair-wise "=="
     * test on each floating-point field in the class (e.g., x, y, and z for a
     * Tuple3d). Since 0.0&nbsp;==&nbsp;-0.0 returns true, we must also return
     * the same hash code for two objects, one of which has a field with a value
     * of -0.0 and the other of which has a cooresponding field with a value of
     * 0.0.
     * 
     * @param d
     *            an input double precision floating-point number
     * @return the integer bits representing that floating-point number, after
     *         first mapping -0.0f to 0.0f
     */
    static long doubleToLongBits(double d) {
        // Check for +0 or -0
        if (d == 0.0) {
            return 0L;
        } else {
            return Double.doubleToLongBits(d);
        }
    }

    /**
     * Returns the representation of the specified floating-point value
     * according to the IEEE 754 floating-point "single format" bit layout,
     * after first mapping -0.0 to 0.0. This method is identical to
     * Float.floatToIntBits(float) except that an integer value of 0 is returned
     * for a floating-point value of -0.0f. This is done for the purpose of
     * computing a hash code that satisfies the contract of hashCode() and
     * equals(). The equals() method in each vecmath class does a pair-wise "=="
     * test on each floating-point field in the class (e.g., x, y, and z for a
     * Tuple3f). Since 0.0f&nbsp;==&nbsp;-0.0f returns true, we must also return
     * the same hash code for two objects, one of which has a field with a value
     * of -0.0f and the other of which has a cooresponding field with a value of
     * 0.0f.
     * 
     * @param f
     *            an input floating-point number
     * @return the integer bits representing that floating-point number, after
     *         first mapping -0.0f to 0.0f
     */
    static int floatToIntBits(float f) {
        if (f == 0.0f) {
            return 0;
        } else {
            return Float.floatToIntBits(f);
        }
    }

    /**
     * Do not construct an instance of this class.
     */
    private VecMathUtil() {
    }
}
